In a time division duplex (Time Division Duplex; TDD) standard of a long term evolution (Long Term Evolution; LTE) system, a radio frame supports multiple different uplink and downlink subframe ratios. For each subframe ratio, the LTE TDD system also defines a delay time kPHICH between the time when a network-side device feeds back an acknowledgement to a user equipment (User Equipment; UE) and the time when the user equipment sends data, that is, defines a timing relation between uplink data transmission and downlink acknowledgement feedback.
The existing LTE LDD system supports a carrier aggregation (Carrier Aggregation) technology, where a user equipment can simultaneously access one or more component carriers (Component Carrier) to perform data communication with a network-side device. Generally a component carrier is also called a serving cell (Serving Cell). When a user equipment simultaneously accesses multiple serving cells, data transmission in serving cell A may be scheduled by a scheduling command sent by serving cell A, that is, self carrier scheduling is performed, or may be scheduled by a scheduling command sent by another serving cell, such as serving cell B, that is, cross-carrier scheduling is performed. When performing cross-carrier scheduling, the network-side device needs to feed back, in a serving cell sending the scheduling command, an acknowledgement for uplink data of the scheduled serving cell to the user equipment.
In the prior art, when a user equipment accesses multiple serving cells with a same subframe ratio, a network-side device occupies a control channel element (Control Channel Element; CCE) resource in an acknowledgement subframe to reserve a physical hybrid automatic repeat request indicator channel (physical HARQ indicator channel; PHICH) resource for each serving cell that is cross-carrier scheduled and sends an acknowledgement for the uplink data over the reserved PHICH resource. An evolved LTE TDD system supports simultaneous access of a user equipment to multiple serving cells with different subframe ratios, and may introduce a new subframe ratio setting for a new function, such as setting some subframes to flexible subframes. When cross-carrier scheduling is performed between serving cells with different subframe ratios, or a new subframe ratio setting is introduced for a new function, how to effectively reserve and allocate a PHICH resource has not been discussed in the prior art.